JP2006084920A - Magnetic toner and two-component developer, and developing device, image forming apparatus and method using toner and developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic toner and a two-component developer for ensuring small deterioration of a carrier by printing, having a long operating life as a developer, and capable of always obtaining images of high image quality, when used in a developing device with a mechanism of autonomously adjusting toner concentration, and to provide a developing device, an image forming apparatus, and an image forming method using the magnetic toner. <P>SOLUTION: The magnetic toner used in a developing device with a mechanism of autonomously adjusting toner concentration comprises at least a binder resin, a magnetic material and a release agent and has a shape factor SF-1 of ≤140, wherein toner particles in which a distance (D<SB>min</SB>) from a toner surface to a magnetic material surface closest to the toner surface is ≤0.1 μm occupy 1 to <50% by number of all toner particles, and wherein a saturation magnetization σs at 398 kA/m is 5-40 Am<SP>2</SP>/kg. The two-component developer, and the developing device, the image forming apparatus, and the image forming method using the toner are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic toner and a two-component developer used in an image forming apparatus using electrophotography such as a copying machine and a printer, a developing device using the same, an image forming apparatus, and an image forming method.

  A number of methods have been conventionally known as electrophotographic processes. In the electrophotographic process, a latent image is electrically formed on the surface of an electrostatic latent image carrier (electrostatic latent image carrier) using a photoconductive substance by various means, and the latent image is formed using toner. After developing and transferring the toner image formed on the surface of the latent electrostatic image bearing member to a transfer medium such as paper with or without an intermediate transfer member, the transfer image is heated, pressurized, and heated. A fixed image is formed through a plurality of steps of fixing by pressurization or solvent vapor. The toner remaining on the surface of the electrostatic latent image carrier is cleaned by various methods as necessary, and the plurality of steps are repeated. Printers and copiers using an electrophotographic process are widely used, and requirements for performance and image quality are becoming stricter year by year.

  The development system in the electrophotographic process is a one-component development system that uses only toner that is colorant particles as a developer, and a magnetic particle (magnetic carrier) called carrier as a developer and toner that is color particles. It is roughly classified into a two-component development system using a thing (two-component developer).

  2. Description of the Related Art Conventionally, as a two-component development type developing device, there are many excellent points such as image quality, cost and stability, so magnetic brush development in which a two-component developer in which toner is mixed in a magnetic carrier is conveyed and developed by a magnetic field. The method is widely used. In this magnetic brush developing method, the toner is carried on the surface of the magnetic carrier by the electrostatic force generated by the friction between the toner and the magnetic carrier. This toner is formed on the surface of the electrostatic latent image carrier. When approaching the latent image, it jumps to the surface of the electrostatic latent image carrier by the electric field formed by this electrostatic latent image, and the electrostatic latent image is visualized. Further, the developer is repeatedly used while replenishing the toner consumed by the development.

  However, in such a magnetic brush developing method, if toner concentration (mixing ratio of toner and magnetic carrier) is not controlled to be within a certain range, toner scattering and fogging occur when the toner concentration increases. On the other hand, when the toner density is reduced, density reduction, density spots, image omission, and the like occur. Therefore, it is necessary to keep the toner density constant in order to obtain a stable image.

  Therefore, in the conventional magnetic brush development method, in order to obtain a stable image, the toner density is detected using a toner density sensor, or a development patch is created on the surface of the electrostatic latent image carrier to detect the toner development amount. In other words, control is performed to keep the toner density constant by appropriately operating the toner supply member in accordance with the signal. For example, the toner density is detected by the toner density sensor, and after determining that the toner density has decreased based on the detection information, the toner supply is performed by the toner supply member.

  However, in this type of magnetic brush developing method, a toner density sensor and a toner replenishing member that can be independently driven ON / OFF are indispensable, and an increase in the size and cost of the developing device cannot be avoided. In addition, there is a problem that the toner density detection system is troublesome, such as creating a density patch to be detected.

  As a prior art for solving such a problem, a developing device that maintains a constant toner density without using a toner density sensor or a toner replenishing member has already been proposed (for example, Patent Document 1 (particularly, pages 1 to 3). And FIG. 1), and Patent Document 2 (especially pages 3 to 6 and FIG. 1)). This type of developing device has a developer accommodating portion that accommodates a two-component developer, and a toner accommodating portion that communicates with the developer accommodating portion and accommodates toner, and the two-component developer on the surface of the developer carrying member The amount is regulated by a regulating member, and the toner concentration is adjusted by autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface of the developer carrying member.

  This autonomous control method generates a developer moving layer carried and conveyed by a developer carrier and a developer circulation layer in which the developer circulates in the developer container, and communicates with the developer container. The toner is taken in from the toner container. That is, when toner is consumed in the development process, the volume of the developer stored in the developer storage unit decreases, and the reduced amount of toner is supplied from the toner storage unit to the developer storage unit. The principle is that the toner concentration of the developer in the developer accommodating portion is kept substantially constant.

  As the toner used in the developing device, a magnetic toner containing a magnetic material can be used. By using the magnetic toner, the toner transportability can be improved by the magnetic force, and the occurrence of scumming can be prevented by the magnetic property of the toner. This is because the toner is caught on the developer carrying member by the magnetic bias, so that only sufficiently charged toner is developed, and insufficiently charged toner is not developed, thereby suppressing the occurrence of soiling. This is considered to be possible.

  However, in the developing system that autonomously controls the toner density as described above, the developing device is divided into the developer containing portion and the toner containing portion, as compared with the conventional two-component developing device, so that the volume of the developer containing portion is reduced. For this reason, the amount of carrier used in the developing device is extremely small as compared with the conventional two-component developing method.

  On the other hand, in recent years, from the viewpoint of further downsizing the apparatus, attempts have been made to save space by reducing the diameter of the developer carrier and the electrostatic latent image carrier. However, in the developing device that autonomously controls the toner density as described above, the amount of carrier is further limited, so that the stress applied to each carrier is further increased.

  In addition to this, the magnetic toner for the magnetic two-component developer contains a magnetic substance, so that the hardness is high, and the magnetic substance is exposed and released on the surface, or the magnetic substance aggregates. Since unevenness is generated on the surface, the stress on the carrier is further increased as compared with the conventional non-magnetic toner.

When a large stress is applied to the carrier, the external additive of the toner moves to the resin coating layer on the surface of the carrier, or the toner itself adheres to the surface of the carrier, and the charging ability deteriorates. Cause defects.
For this reason, as compared with the non-magnetic two-component developing method, there are problems that the life of the carrier is extremely short, the reliability of the image is lowered, the carrier is frequently replaced, and the running cost is high.

  For example, in Patent Document 3, the magnetic toner has a particle size distribution of a weight average particle size of 6.0 to 10.0 μm, 5 to 60% by number of magnetic toner particles of 5 μm or less, and 12.7 μm or more. The magnetic toner particles are 2% by volume or more, the magnetization in a magnetic field of 5 kOe (= 398 kA / m) is 10 to 25 emu / g, and the magnetic carrier is a core containing at least a silicone resin as a main component. A developer characterized by having a layer is disclosed. This can extend the carrier life, but is insufficient because the level of stress on the carrier does not change due to the exposure of the magnetic material on the toner surface and the surface irregularity of the toner. Further, since the magnetic toner particles of 12.7 μm or more are contained in an amount of 2% by volume or more, the image quality is inferior and the demand for high image quality cannot be satisfied.

Patent Document 4 discloses that in an electrostatic charge image developing toner containing at least magnetic fine particles and a binder resin, the magnetic fine particles are not present on the surface of the toner, and b _min /A>0.02. An electrostatic charge image developing toner characterized by satisfying (where A is the average particle diameter of the toner and b _min is the distance between the magnetic fine particles located closest to the toner surface and the toner surface) is disclosed. Yes. As a result, the magnetic substance exposed on the surface disappears, and the stress applied to the carrier is reduced. However, since there is no magnetic substance near the surface, the external additive is applied to the toner due to the stress inside the developing device. The embedding is promoted, causing charging failure and image quality is deteriorated.
Therefore, in the current situation, the technology described in the above literature cannot obtain a sufficiently satisfactory improvement effect in response to the demands for downsizing, high reliability, and cost reduction of the apparatus.

Japanese Patent Publication No. 5-67233 JP 2000-352877 A JP 2002-287418 A JP-A-7-209904

  The image forming method using the magnetic two-component developer using the developing device having the mechanism for adjusting the toner concentration autonomously as described above is compared with the two-component developing method including a normal toner concentration sensor. Thus, the developer life is short, and the stability and reliability of the image are insufficient.

Therefore, in view of the above problems, the present invention does not require a toner density detection mechanism using a toner density sensor or a toner patch, or a special toner replenishment mechanism, and is a compact type having a mechanism for adjusting the toner density autonomously. Magnetic toner and two-component developer capable of always obtaining a high-quality image with little deterioration of the carrier due to printing, long life as a developer when used in a low-cost development device, and image formation It aims to provide a method.
It is another object of the present invention to provide a developing device, an image forming apparatus, and an image forming method that can realize the demands for downsizing, high reliability, and low cost on a high level by using the magnetic toner or the two-component developer. .

  In order to solve the above problems, the present inventors have intensively studied the factors for stabilizing the toner density in a developing device having a mechanism for autonomously adjusting the toner density, and as a result, the shape of the toner and the toner inside It was found to be related to the dispersion state of the magnetic material. That is, by controlling the shape of the toner and the dispersion state of the magnetic material inside the toner, it has been found that the stress on the carrier can be reduced and the life of the developer can be extended, leading to the present invention.

That is, the present invention
<1> A developer carrying member that has a magnetic field generating means therein and conveys and carries a two-component developer containing toner and a magnetic carrier; a developer containing unit that supplies the developer to the developer carrying member; A toner container that communicates with the developer container and contains toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, and the developer carrier A toner used in a developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface,
A magnetic toner containing at least a binder resin, a magnetic material, and a release agent;
Its shape factor SF-1 is 140 or less,
The toner having a distance (D _min ) from the toner surface to the nearest magnetic material surface of 0.1 μm or less is 1% by weight or more and less than 50% by weight in all toners,
The saturation magnetization σs at 398 kA / m is 5 to 40 Am ² / kg,
It is a magnetic toner characterized by being.

<2> The magnetic toner according to <1>, wherein a surface wax amount by XPS is 5 to 40%.
<3> The magnetic toner according to <1 or 2>, wherein the magnetic toner is manufactured by a wet manufacturing method.

<4> A developer carrying member that has a magnetic field generating means therein and conveys and carries a two-component developer containing toner and a magnetic carrier, a developer container that supplies the developer to the developer carrying member, A toner container that communicates with the developer container and contains toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, and the developer carrier A two-component developer used in a developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface,
A two-component developer, wherein the toner contained is the magnetic toner according to any one of <1> to <3>.

<5> A developer carrying member that includes a magnetic field generating means and transports and carries a two-component developer containing toner and a magnetic carrier; a developer containing unit that supplies the developer to the developer carrying member; A toner container that communicates with the developer container and contains toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, and the developer carrier A developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface;
The developing device according to any one of <1> to <3>, wherein the toner accommodated in the toner accommodating portion is the magnetic toner according to any one of <1> to <3>.

<6> At least the latent image forming means for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the two-component developer containing toner and magnetic carrier contained in the developing device. A developing unit that visualizes the latent image and forms a toner image on the surface of the electrostatic latent image carrier, and a transfer unit that transfers the formed toner image to the surface of the transfer target. An image forming apparatus,
The developing device in the developing means includes a developer carrying body having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier, and development for supplying the developer to the developer carrying body A developer container, and a toner container that communicates with the developer container and accommodates toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, A developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface of the developer carrying member, and is accommodated in the toner accommodating portion. An image forming apparatus, wherein the toner is the magnetic toner according to any one of <1> to <3>.

<7> Further, a cleaning unit that cleans the surface of the electrostatic latent image carrier after the transfer by the transfer unit, and collects toner remaining on the surface of the electrostatic latent image carrier;
<6> The image forming apparatus according to <6>, further including a toner returning unit that conveys the collected toner to the developing device.

<8> A developer carrier having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier, a developer container for supplying the developer to the developer carrier, A toner container that communicates with the developer container and contains toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, and the developer carrier An image forming method using a developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner density of the two-component developer on the surface,
An image forming method, wherein the toner is the magnetic toner according to any one of <1> to <3>.

<9> a latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
A developing step of forming the toner image on the surface of the electrostatic latent image carrier by visualizing the formed latent image with a two-component developer containing toner and magnetic carrier contained in the developing device. When,
A transfer step of transferring the formed toner image onto the surface of the transfer target;
A cleaning step of cleaning the surface of the latent electrostatic image bearing member after transfer to recover toner remaining on the surface of the latent electrostatic image bearing member;
<8> The image forming method according to <8>, further comprising a toner returning step of conveying the collected toner to the developing device.

  Since the magnetic toner of the present invention has an appropriate shape, dispersion state of the magnetic material inside the toner, and saturation magnetization, the magnetic toner or a two-component developer containing the magnetic toner is autonomously adjusted. By using the developing device having a mechanism, the stress on the carrier is reduced and the life of the developer can be extended. Further, by using the magnetic toner of the present invention or the two-component developer containing the magnetic toner, a highly reliable developing device, image forming apparatus, and image forming method can be provided.

Hereinafter, the present invention will be described in detail.
[Developer]
In the developing device of the present invention, first, a developer carrying member having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier, and supplying the developer to the developer carrying member. A developer container, and a toner container that communicates with the developer container and accommodates toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member. A mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface of the developer carrying member (hereinafter sometimes referred to as “autonomous toner concentration control mechanism”). (The basic configuration of the developing device excluding the developer described above may be referred to as a “developing device main body”). The toner of the two-component developer accommodated in the developing device main body is specific to the present invention. This point will be described in detail in the section of [Toner].
In the developing device of the present invention, the developer accommodating portion and the toner accommodating portion may be appropriately partitioned inside, and the shape thereof is not limited.

A developing device which is an example of the present invention having an autonomous toner density control mechanism is shown in FIG.
As shown in FIG. 1, the developing device main body 15 of the present example includes a fixed magnet 1 as a magnetic field generating means fixed inside, and rotates and conveys a two-component developer 2 containing toner and a magnetic carrier. A developer carrying member 3 to be carried, a first developer containing portion 4a for containing the two-component developer 2 adjacent to the developer carrying member 3, and a developer carrying member 3 via the first developer containing portion 4a. A second developer containing portion 4b, which is provided in communication with the developer carrying member 3 so as to be able to supply a developer having a higher toner concentration than the developer carried on the developer carrying member 3, and the first developer containing portion 4a and the first developer containing portion. A toner container 5 provided in communication with the developer carrier 3 through the two developer containers 4b and for accommodating toner so as to be supplied to the second developer container 4b; and adjacent to the developer carrier 3. In addition, the developer carrying direction of the developer carrier 3 with respect to the first developer container 4a ( The developer retracting portion 7 is provided on the downstream side and communicates with the first developer accommodating portion 4a, and the developer carrier 3 is developed with respect to the first developer accommodating portion 4a and the developer retracting portion 7. A part of the two-component developer 2 carried and conveyed by the developer carrier 3 is dammed as an excess developer, and the first developer accommodating portion 4a or the developer is retracted according to the toner concentration. The section 7 includes a damming section (developer separating means) 8 for separating the excess developer. The two-component developer 2 separated into the developer retracting portion 7 flows out to the second developer accommodating portion 4b.

  The behavior of the two-component developer 2 in the vicinity of the damming portion 8 will be described. First, it is assumed that the toner density of the two-component developer 2 carried and conveyed by the developer carrier 3 is low. Since the two-component developer 2 has a small amount of toner in the developer, the magnetic carrier density per unit volume is relatively large. That is, since the magnetic attraction force received by the two-component developer 2 from the external magnetic field increases, the two-component developer 2 having a low toner concentration is reliably conveyed to the vicinity of the damming portion 8. The two-component developer 2 that has been reliably conveyed to the damming portion 8 pushes out the staying developer staying in the vicinity of the damming portion 8 by the damming force and magnetic restraining force of the damming portion 8, and the accumulated developer thus pushed out. The developer falls as a falling developer, travels along the upper surface of the partition portion 12, falls to the developer retracting portion 7, and flows into the second developer accommodating portion 4 b via the developer retracting portion 7.

  At this time, when the two-component developer 2 having a low toner concentration is guided to the developer retracting portion 7 as described above, a space is created in the first developer accommodating portion 4a. As a result, the two-component developer 2 that has been in the developer supply path from the developer supply port 6 to the first developer accommodating portion 4a is separated from the space by the conveying force of the stirring member and the weight of the two-component developer. The two-component developer near the developer supply port 6 flows quickly. As a result, the developer supply port 6 receives the two-component developer 2 having a high toner concentration from the second developer accommodating portion 4b, and the two-component developer G having the high toner concentration is received by the first developer accommodating portion 4a. Will be supplied promptly. Further, a space for receiving toner from the toner storage portion 5 is formed by the amount of developer supplied with a high toner concentration, and the toner T in the developer supply port 6 rotates the developer stirring member 10 in the direction of arrow B. The toner is quickly supplied to the second developer accommodating portion 4b by pulling in by driving, the weight of the toner T, and sweeping out by rotating the toner stirring member 11 in the direction of arrow C.

  On the other hand, assuming that the toner concentration of the two-component developer 2 carried and conveyed by the developer carrier 3 is high, the two-component developer 2 has a relatively large amount of toner covering the surface of the magnetic carrier. The magnetic carrier density per unit volume is small. That is, since the magnetic attraction force received by the two-component developer 2 from the external magnetic field is small, most of the two-component developer 2 having a high toner concentration is more than the tip of the partition 12 with respect to the rotation direction of the developer carrier 3. It falls at the upstream position. As a result, the two-component developer 2 does not reach the staying developer staying in the vicinity of the damming section 8 and does not fall to the developer retracting section 7 along the upper surface of the partition section 12. For this reason, the two-component developer 2 falls at a position upstream from the tip of the partition 12 with respect to the rotation direction of the developer carrier 3 and directly returns to the first developer accommodating portion 4a.

  At this time, unlike the case where the toner concentration is low, no space is created in the first developer accommodating portion 4a, and the two-component developer 2 near the developer supply port 6 does not flow. The two-component developer 2 having a high toner concentration is not supplied from the second developer accommodating portion 4b. Similarly, no space for receiving the toner T from the toner storage unit 5 is formed in the second developer storage unit 4b, and thus the toner T is not supplied.

  As described above, the autonomous toner concentration control mechanism uses the change in fluidity or bulk of the two-component developer 2 according to the toner concentration, and the two-component developer 2 having a low toner concentration. The toner is replenished and is controlled autonomously so that toner replenishment is not performed for the two-component developer 2 having a high toner concentration.

Thus, the two-component developer 2 that is autonomously controlled to an appropriate toner concentration and carried on the developer carrier 3 is an electrophotographic photosensitive member (electrostatic latent image carrier) that is a member of the image forming apparatus. 9 is conveyed to a position opposite to 9. An image-like electrostatic latent image is previously formed on the surface of the electrophotographic photosensitive member 9, and toner is transferred to the electrostatic latent image and developed (development process).
Processes and configurations before and after the development process will be described in the sections [Image forming apparatus] to [Image forming method].

[toner]
The magnetic toner of the present invention (hereinafter sometimes simply referred to as “toner”) used in the developing device main body having the autonomous toner concentration control mechanism as described above is based on the presence state of the magnetic substance in the vicinity of the toner surface. By controlling the toner shape and saturation magnetization within an appropriate range, the stress on the carrier is reduced, and the life of the developer can be extended even with a small amount of carrier.
Hereinafter, (shape, presence state and physical properties of magnetic substance), (manufacturing method), and (composition component) will be described in this order.

(Shape, presence of magnetic materials and physical properties)
The magnetic toner of the present invention has a shape factor SF-1 of 140 or less as a shape, and a distance (D _min ) from the toner surface to the nearest magnetic material surface is 0.1 μm or less as the presence state of the magnetic material. The toner is characterized by having a saturation magnetization σs of 5 to 40 Am ² / kg at 398 kA / m as a physical property.

The reason why the life of the developer can be extended by controlling the presence state of the magnetic substance in the vicinity of the toner surface and the toner shape within an appropriate range is not clear, but is estimated as follows.
First, as the shape factor SF-1 of the toner increases, the unevenness of the toner surface increases and sharp portions increase. When the toner and the carrier collide with each other at an acute angle portion, the pressure applied to the toner increases because the contact area is small. At this time, the external additive on the toner surface is transferred to or detached from the carrier, so that the carrier is contaminated. Further, when the pressure is higher, the toner is fused to the carrier surface. Therefore, as the shape factor SF-1 increases, the collision frequency at such a large pressure increases and the carrier life is deteriorated. However, by controlling the toner to a shape with less surface irregularities, the life of the carrier is extended. It is considered possible.

  In addition, when there is a magnetic material near the surface of the toner, the location where the magnetic material is located tends to be a convex portion, in which case it collides with the carrier when the binder resin layer is thin or the magnetic material is exposed. In this case, a greater stress is applied as compared with the collision with the toner having no magnetic material near the surface. For this reason, since the life of the carrier is reduced due to the presence of a large amount of magnetic material in the vicinity of the toner surface, it is considered that the decrease in the carrier life can be prevented by controlling the state of the magnetic material on the toner surface.

In the magnetic toner of the present invention, the toner whose distance D _min from the toner surface to the closest magnetic surface is 0.1 μm or less is 1% or more and less than 50% by number of all toners.
This “distance D _min from the toner surface to the closest magnetic material surface” (hereinafter sometimes simply referred to as “distance D _min ”) can be obtained as follows.

  First, toner particles to be observed are sufficiently dispersed in a room temperature curable epoxy resin and then cured in an atmosphere at a temperature of 40 ° C. for 2 days to obtain a cured product. The obtained cured product is formed into a flake by a microtome equipped with diamond teeth and used as a sample. This sample is photographed with a transmission electron microscope (TEM).

Specifically, the ratio of the toner whose distance D _min is 0.1 μm or less is determined as follows. Distance is D _min determined subject to the toner particles, determined circle equivalent diameter from the cross-sectional area of the photomicrographs, select only those whose values are included in ± 10% of the width of the number average particle diameter D _1. The minimum value ( _Dmin ) of the distance with the particle | grain surface of a magnetic body is measured about the applicable particle | grain on a TEM photograph.
As described above, the toner is obtained with respect to 100 toner particles while changing the visual field, and the ratio of particles having a D _min of 0.1 μm or less in the 100 toner particles is obtained. At this time, in order to accurately measure D _min , it is preferable to use a photograph with a magnification of 10,000 to 20,000 times.

In the present invention, a transmission electron microscope (JEM1010 manufactured by JEOL Ltd.) was used as an apparatus, observed at an acceleration voltage of 80 kV, and observed / measured using a microphotograph having an enlargement magnification of 15,000 times. Of course, the measurement may be performed with other apparatuses and conditions.
The equivalent circle diameter of the toner particles was determined by analyzing a micrograph using an image analyzer LUZEX III (manufactured by Nireco).
The number average particle diameter D ₁ is Coulter Counter Model TA-II as a measurement apparatus - (manufactured by Beckman Coulter, Inc.) using an electrolytic solution ISOTON-II - was used (Beckman Coulter).

  The method for measuring the particle size is as follows. 0.5 to 50 mg of a measurement sample is added to 2 ml of an aqueous solution of a surfactant as a dispersant, preferably 2 ml of a 5% aqueous solution of sodium alkylbenzenesulfonate. This is added to 100 to 150 ml of the electrolytic solution. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the particle size distribution of 2 to 60 μm particles is measured using the Coulter counter TA-II type with an aperture diameter of 100 μm. Volume average distribution and number average distribution. The number of particles to be measured is 50,000.

When the ratio of particles having a distance D _min of 0.1 μm or less is less than 1%, the external additive is easily embedded in the toner, and the chargeability is deteriorated, resulting in a decrease in image density and toner scattering. . When the ratio of particles having a distance _Dmin of 0.1 μm or less is 50% or more, the life of the carrier is reduced due to the stress caused by the magnetic substance in the vicinity of the surface.
The distance _Dmin is more preferably 2% by number or more and less than 40% by number, and further preferably 4% by number or more and less than 35% by number.

  In the present invention, the shape factor SF-1 of the toner needs to be 140 or less, preferably 110 or more and 140 or less. When SF-1 is larger than 140, the degree of toner irregularity increases, so that the stress with the carrier increases and the life of the developer decreases. The lower limit of SF-1 is not particularly limited. However, if it is smaller than 110, toner cleaning becomes difficult and image defects due to poor cleaning are likely to occur, which is not preferable. The toner shape factor SF-1 is more preferably 114 to 138, and still more preferably 118 to 136.

Here, the toner shape factor SF-1 is an index representing the degree of toner sphere. The closer the shape factor SF-1 is to 100, the closer it is to a sphere. In the true sphere, the shape factor SF-1 is 100. Become. Specifically, it is represented by the following formula (1).
SF-1 = (π / 4 ) × (ML 2 / A) × 100 ··· (1)
ML: Maximum length of the diameter in the projected image of the toner A: Projected area in the projected image of the toner

The toner shape factor SF-1 in the present invention is obtained, for example, as follows.
First, the toner to be measured is spread on the slide glass, and the optical microscope image is taken into an image analyzer (for example, Image Analyzer LUZEX III manufactured by Nireco) via a video camera. Then, with respect to 100 or more toners, the maximum diameter length (ML) and the projection area (A) in the projected image are measured. From the measurement result, the above formula (1) is calculated to obtain the average value, and the obtained value is defined as the toner shape factor SF-1.

In the magnetic toner of the present invention, the volume average particle diameter D _50v is preferably 4 μm or more and 10 μm or less. When the volume average particle diameter D _50v is _less than 4 μm, the chargeability tends to be insufficient, the developability may be lowered, and when it exceeds 10 μm, the resolution of the image may be lowered.
The volume average particle diameter D _50v of the toner is measured using a measuring instrument such as Coulter Counter TAII (Beckman-Coulter) or Multisizer II (Beckman-Coulter) as described above. Can do.

In the magnetic toner of the present invention, the saturation magnetization σs at 398 kA / m (5 kOe) is required to be in the range of 5 to 40 Am ² / kg, and the content of the magnetic material is controlled so as to be in this range. When the saturation magnetization [sigma] s is less than 5 Am < ² > / kg, the toner trapping force by the magnetic bias is not sufficient, so that the effect of preventing soiling cannot be obtained, which is not preferable. On the other hand, when it exceeds 40 Am ² / kg, since the magnetic bias is too large, the developability is extremely deteriorated and a sufficient image density cannot be obtained. Furthermore, if it exceeds 40 Am ² / kg, the specific gravity of the toner increases, and the stress on the carrier becomes too large, which is not preferable.

In the magnetic toner of the present invention, the saturation magnetization σs at 398kA / m (5kOe), preferably in the range of 8~35Am ² / kg, and more preferably in a range of from 10~30Am ² / kg.
In the present invention, a vibrating sample magnetometer VSM-P10 manufactured by Toei Kogyo Co., Ltd. was used to measure the saturation magnetization σs. Of course, you may measure with another apparatus.

The toner distance D _min , the shape factor SF-1, the particle size, and the saturation magnetization σs described above are the values before the external additive is added when the external additive described later is added. The toner base particles (generally referred to as “toner particles”, “colored particles”, etc.) are discussed.

(Production method)
The magnetic toner satisfying the above criteria of the distance D _min from the toner surface to the nearest magnetic surface, the shape factor SF-1 and the saturation magnetization σs at 398 kA / m (5 kOe) is preferably produced by a wet manufacturing method. Conventionally, as a method for producing a toner used in electrophotography, a kneading and pulverizing method, which is a method of obtaining a toner having a desired particle diameter by melting and kneading a toner compounding component and then pulverizing, is particularly preferable. It is extremely difficult to control the presence state of the surface material by the kneading and pulverizing method. On the other hand, the wet manufacturing method is preferable because it is suitable for controlling the shape and structure of the toner (position and amount of the magnetic substance).

  As the wet manufacturing method, a known method can be used. For example, suspension polymerization methods described in JP-A-59-53856 and JP-A-59-61842 may be used. Further, a binder resin, a colorant, and a release agent disclosed in Japanese Patent No. 3417212 are added to an oily medium to obtain an oily dispersion mixture, and the oily dispersion mixture is dispersed in an aqueous medium. A manufacturing method may be used in which oil droplets are formed and the oily medium is removed from the oil droplets to form toner particles. Further, an emulsion aggregation method disclosed in Japanese Patent Application Laid-Open Nos. 63-2822752 and 6-250439 may be used.

In particular, the emulsion aggregation method described below is more preferably used from the viewpoint of easy control of toner shape and surface structure.
In the emulsion aggregation method, a resin dispersion using an ionic surfactant is mixed with a magnetic substance, a colorant, a release agent, etc. dispersed in an ionic surfactant of the opposite polarity to cause hetero-aggregation, thereby reducing the toner diameter. Agglomerated particles are formed (aggregation process), and then heated to the glass transition point Tg or higher of the resin to fuse and aggregate (unify) the aggregated particles (fusion process), and are washed and dried to produce a toner. Is done. This method makes it possible to easily reduce the toner particle size and not only to obtain a sharp particle size distribution, but also to control the shape and structure (position and amount of magnetic substance).

  Specifically, for example, it can be easily produced by the following method. That is, a resin fine particle dispersion in which resin fine particles of at least 1 μm or less obtained by emulsion polymerization or the like are dispersed with an ionic surfactant, and a magnetic particle dispersion dispersed with an ionic surfactant having the opposite polarity, The colorant dispersion and the release agent dispersion are mixed. Moreover, you may further mix a charge control agent dispersion liquid as needed. These are mixed to cause heteroaggregation to form aggregated particles corresponding to the toner diameter. Subsequently, the prepared aggregated particle dispersion is heated to a temperature equal to or higher than the glass transition point Tg of the resin, fused and united, washed and dried to obtain toner particles.

  In the agglomeration step, the initial balance of the amount of the ionic surfactant of each polarity is shifted in advance, and after forming and stabilizing the first-stage base aggregated particles below the glass transition point, the second stage Add a fine particle dispersion treated with a polar and quantity surfactant so as to compensate for the balance deviation, and if necessary, below the glass transition point of the resin contained in the base aggregated particles or additional fine particles After being heated and stabilized slightly, the fine particles added in the second stage can be fused while adhering to the surface of the base aggregated particles by heating above the glass transition point. In addition, these agglomeration operations can be repeated several times stepwise, and as a result, the composition and physical properties can be changed stepwise from the surface to the inside of the toner particles, thereby controlling the toner structure. Is extremely easy. Therefore, it is easy to manufacture the toner so that the structure (existing position / amount of the magnetic substance) satisfies the conditions defined in the present invention.

In this method, the distance D _min , the shape factor SF-1, and the saturation magnetization σs are controlled by changing the amount of the fine particle dispersion added and mixed later, the heating temperature, the heating time, and the pH adjustment in the toner fusion. It becomes possible. Further, since the toner fusion conditions vary depending on the amount of magnetic material (magnetic powder) added, the toner fusion conditions may be adjusted according to the amount of magnetic material.

(Compounding ingredients)
The magnetic toner of the present invention is a magnetic toner containing at least a binder resin, a magnetic material, and a release agent. In addition, an external additive, an internal additive, a colorant, and the like can be appropriately contained as necessary. Hereinafter, each component will be described.

: Binder resin:
The binder resin used in the production of the magnetic toner of the present invention is not particularly limited. For example, styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, and acrylic acid n- Esters having a vinyl group such as propyl, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; Vinyl nitriles such as acrylonitrile and methacrylonitrile; Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; Ethylene, propylene, butadiene, etc. Polymers or copolymers obtained by combining them two or more made of monomers such as Li olefins, can further be used mixtures thereof. In addition, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, etc., non-vinyl condensation resins, or mixtures thereof with the vinyl resins, or vinyl monomers in the presence of these resins Graft polymers obtained by polymerizing can be used.

  The glass transition point Tg of the resin fine particles is preferably 40 to 80 ° C. from the viewpoint of reduction of toner production energy, toner storage stability, shape controllability, low-temperature fixability, image storage stability, and the like. It is preferable that it is 45-70 degreeC. By setting the glass transition point Tg in the range, an inexpensive high-quality toner that satisfies the above characteristics can be provided.

: Magnetic material:
The magnetic toner of the present invention contains a magnetic material. Owing to the magnetism of the toner, it is possible to prevent the occurrence of soiling. This is because the toner is caught on the developer carrier by the magnetic bias, so that only sufficiently charged toner is developed, and insufficiently charged toner is not developed. This is thought to be possible.

Examples of the magnetic material used in the present invention include known magnetic materials such as metals such as iron, cobalt and nickel and alloys thereof, Fe ₃ O ₄ , γ-Fe ₂ O ₃ , and metal oxides such as cobalt-added iron oxide. And various ferrites such as MnZn ferrite and NiZn ferrite, magnetite, hematite and the like can be used. Further, the surface of these magnetic materials may be treated with a surface treatment agent such as a silane coupling agent or a titanate coupling agent, coated with an inorganic material such as a silicon compound or an aluminum compound, or polymer coated. .

The content of the magnetic powder is preferably in the range of 5 to 50% by mass, more preferably in the range of 10 to 40% by mass with respect to the total toner particles. If the content of the magnetic material is less than 5% by mass, the toner trapping force by the magnetic bias may be insufficient, and it is difficult to obtain the effect of preventing scumming. On the other hand, if it exceeds 50% by mass, the magnetic bias is too large and the developability tends to deteriorate, making it difficult to obtain a sufficient image density.
These magnetic materials having a number average particle diameter of about 0.05 to 0.35 μm are preferably used from the viewpoint of dispersibility in the binder resin.

:Release agent:
The magnetic toner of the present invention contains a release agent to prevent the occurrence of offset.
In the magnetic toner of the present invention, the surface wax amount (exposure amount of the release agent on the toner surface) by an X-ray photoelectron spectrometer (XPS) is preferably in the range of 5 to 40%.

  The exposure amount (surface wax amount) of the release agent on the toner surface can be quantified by photoelectron spectroscopy (XPS). In this method, first, the individual spectra of the binder resin and the release agent among the materials constituting the toner are measured, and the spectrum obtained from the measurement of the toner particles is fitted with each individual spectrum. The surface exposure rate of the release agent in each toner particle is determined. In this invention, it is preferable to make the element ratio (namely, surface wax amount) resulting from this mold release agent in the range of 5 to 40%.

  When a large amount of release agent is present on the surface, toner tends to adhere to the carrier, so that the charging ability of the carrier is likely to deteriorate. In addition, external additives are likely to be embedded inside the toner due to stress caused by stirring with the carrier in the developing device, so that toner fluidity and charging defects are likely to occur, causing problems such as image density reduction. It becomes easy to do. On the other hand, when the surface amount of the release agent decreases, the release agent does not ooze out to the toner surface during heat fixing, and the offset prevention effect is hardly exhibited.

  In order to suppress any problems related to carrier deterioration, image density reduction and offset as described above, the amount of surface wax is preferably in the range of 5 to 40% as described above, and 8 to 35%. More preferably, it is more within the range of 10 to 30%.

  There are no particular limitations on the release agent that can be used in the present invention, and conventionally known release agents can be used without any problem. Specific examples include low molecular weight polyolefins such as polyethylene, polypropylene, polybutene; silicones that exhibit a softening point upon heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid amide; Plant waxes such as Uba wax, rice wax, candelilla wax, tree wax, jojoba oil; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, etc. Minerals and petroleum waxes; and their modifications may be used and exemplified.

  The content of the release agent is preferably in the range of 0.1 to 20% by mass, more preferably in the range of 2 to 15% by mass with respect to the whole toner particles. If the content of the release agent is less than the above lower limit value, the toner release performance may be reduced and offset may occur. On the other hand, if the content exceeds the upper limit value, the toner charging performance is deteriorated or the heat storage performance is increased. May occur, which is not preferable.

: External additive:
In the magnetic toner of the present invention, various inorganic or organic fine particles are preferably externally added to the toner as necessary for the purpose of improving durability and powder flowability.
Examples of inorganic fine particles that can be used as an external additive include silica, aluminum oxide, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, silica Apatite, diatomaceous earth, cerium chloride, bengara, chromium oxide, cerium oxide, antimony trioxide, magnesium oxide, magnesium carbonate, zirconium oxide, silicon carbide, silicon nitride, calcium carbonate, barium sulfate and other metal oxides and ceramic particles Can be mentioned.
These inorganic fine particles preferably have a primary particle size of about 5 nm to 500 nm.

Moreover, it is preferable that these inorganic fine particles are hydrophobized. When the inorganic fine particles subjected to the hydrophobic treatment are used, the charge amount of the toner under high humidity can be improved, and as a result, the environmental stability of the chargeability of the toner can be improved.
Hydrophobizing agents that can be used for the hydrophobizing treatment include coupling agents such as silane coupling agents, titanate coupling agents, aluminate coupling agents, zirconium coupling agents, silicone oils and polymers. Examples include coating treatment. These hydrophobizing agents can be used alone or in combination.

  In addition to the inorganic fine particles, organic fine particles can be externally added to the toner. Examples of the organic fine particles include vinyl polymers such as styrene polymers, (meth) acrylic polymers, and ethylene polymers, and various polymers such as ester, melamine, amide, and allyl phthalate. Fluoropolymers such as vinylidene fluoride and fine particles composed of higher alcohols such as unilin can be mentioned, and those having a primary particle size of 0.05 to 7.0 μm are preferably used. The organic fine particles are generally added for the purpose of improving cleaning properties and transferability.

When inorganic fine particles or organic fine particles are added to the toner, these fine particles can be adhered or fixed to the surface of the toner particles by applying a mechanical impact force together with the toner particles using a sample mill or a Henschel mixer.
The amount of external additive added varies depending on the type and combination of external additives and various properties, shapes, and blends of toner base material particles (toner particles). When the base material particle (toner particle) is 100 (mass basis), it is selected from the range of about 0.1 to 5.0.

: Internal additive:
Various substances may be added as internal additives to the magnetic toner of the present invention for the purpose of charge control. For example, high molecular acids such as fluorosurfactants, salicylic acid complexes, iron dyes such as iron complexes, chromium dyes such as chromium complexes, and copolymers containing maleic acid as a monomer component, quaternary Azine dyes such as ammonium salts and nigrosine may be added in the range of 0.1 to 10.0% by mass.

: Colorant:
The magnetic toner of the present invention may be used in combination with a colorant other than the magnetic material described above for adjusting the coloring power. Examples of black colorants that can be used include black iron hydroxide, black titanium oxide, and carbon black.

  Moreover, in order to adjust a color tone, you may contain coloring agents other than black. There is no restriction | limiting in particular as a coloring agent which can be used, A well-known coloring agent can be mentioned, According to the objective, it can select suitably. Examples of such colorants include DuPont oil red, Orient oil red, Rose Bengal, C.I. I. Pigment Red 5, 112, 123, 139, 144, 149, 166, 177, 178, 222, 48: 1, 48: 2, 48: 3, 53: 1, 57: 1 and 81: 1, C.I. I. Pigment Orange 31 and 43, quinoline yellow, chrome yellow, C.I. I. Pigment Yellow 12, 14, 17, 93, 94, 97, 138, 174, 180 and 188, ultramarine blue, aniline blue, calcoyl blue, methylene blue chloride, copper phthalocyanine, C.I. I. Pigment Blue 15, 60, 15: 1, 15: 2 and 15: 3, C.I. I. Pigment Green 7 and Malachite Green Oxalate can be used, and these can be used alone or in combination.

The toner described above exists as a two-component developer together with the magnetic carrier in the developing device main body, particularly in the developer container.
The magnetic carrier used in the present invention (hereinafter sometimes simply referred to as “carrier”) is not particularly limited, and examples thereof include well-known carriers. A known carrier such as a resin-coated carrier described in Japanese Patent Laid-Open No. 56-11461 can be used.

  Specific examples of the carrier include the following resin-coated carriers. That is, examples of the core particle of the carrier include normal iron powder, ferrite, magnetite molding, and the like, and the volume average particle size is preferably in the range of about 30 to 200 μm.

  Examples of the coating resin for the core particles include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, and 2-ethylhexyl acrylate. Α-methylene fatty acid monocarboxylic acids such as methyl methacrylate, methacrylic acid and n-propyl lauryl methacrylate 2-ethylhexyl; nitrogen-containing acrylics such as dimethylaminoethyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile Vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; Ketones; olefins such as ethylene and propylene; vinyl-based fluorine-containing monomers such as vinylidene fluoride, tetrafluoroethylene, and hexafluoroethylene; homopolymers such as, or copolymers composed of two or more types of monomers, Examples include silicones such as methylsilicone and methylphenylsilicone; polyesters containing bisphenol and glycol; epoxy resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and polycarbonate resins. These resins may be used alone or in combination of two or more.

The amount of the coating resin is preferably in the range of about 0.1 to 10 parts by mass and more preferably in the range of 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the core particles.
For the production of the carrier, a heating kneader, a heating Henschel mixer, a UM mixer, or the like can be used. Depending on the amount of the coating resin, a heating fluidized rolling bed, a heating kiln, or the like can be used. it can.

  The two-component developer in the present invention is produced by mixing the magnetic carrier and toner described above. As the mixing ratio, although it cannot be generally stated, an optimum value is selected from the range of about 1:99 to 40:60 for toner: magnetic carrier (mass ratio). According to the developing device, the image forming apparatus, and the image forming method of the present invention using the two-component developer, the stress on the carrier is reduced and the life of the developer can be extended.

[Image forming apparatus]
The image forming apparatus of the present invention includes at least a latent image forming unit that forms an electrostatic latent image on the surface of an electrostatic latent image carrier, and a two-component developer including toner and a magnetic carrier accommodated in the developing device. Developing means for visualizing the formed latent image and forming a toner image on the surface of the electrostatic latent image carrier, and transfer for transferring the formed toner image to the surface of the transfer target An image forming apparatus comprising:
The developing device in the developing means includes a developer carrying body having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier, and development for supplying the developer to the developer carrying body A developer container, and a toner container that communicates with the developer container and accommodates toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, A developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the two-component developer on the surface of the developer carrying member, and is accommodated in the toner accommodating portion. The toner is the magnetic toner of the present invention described above.

The image forming apparatus of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic sectional view showing an electrophotographic apparatus which is an example of the image forming apparatus of the present invention.
An electrophotographic apparatus shown in FIG. 2 includes an electrophotographic photosensitive member (electrostatic latent image carrier) 109, a charger (charging means) 111 that charges the surface of the electrophotographic photosensitive member 109, and an electrophotographic photosensitive member 109. An image input device (electrostatic latent image forming means) 113 that forms an electrostatic latent image on the surface, and a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor 109 with toner to obtain a toner image (Developing means) 115, a transfer device (transfer means) 114 for transferring the formed toner image to the surface of the transfer target 120 such as paper, and a cleaning blade 119 remove residual toner and the like on the surface of the electrophotographic photosensitive member 109. A cleaning device (cleaning means) 116 for removing the residual potential on the surface of the electrophotographic photosensitive member 109, and a toner image transferred to the surface of the transfer target 120 with heat and / or Has a fixing device (a fixing means) 118 for fixing the force, etc., the.

In this example, the developing device (developing means) 115 is the developing device of the present invention, and the developing device main body 15 in FIG. 1 is used as it is. The toner T to be accommodated is the magnetic toner of the present invention and is as described above.
In addition, the configurations of the charger 111, the image input device 113, the transfer device 114, the static eliminator 117, and the fixing device 118 are not particularly limited in the present invention, and any configuration conventionally known in the electrophotographic field is applied as it is. be able to. Note that in the case of the configuration using the contact charging type charger 111 as in this example, the static eliminator 117 is not necessarily provided.

  The image forming method of the present invention will be described using the electrophotographic apparatus of FIG. The surface of the electrophotographic photosensitive member 109 is uniformly charged by the charger 111, and an electrostatic latent image is formed by the image input device (electrostatic latent image forming means) 113 (latent image forming step). The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 109 is visualized by toner built in the developing device (developing means) 115 to form a toner image (developing process). The toner image formed on the surface of the electrophotographic photosensitive member 109 is transferred to the surface of the transfer target 120 inserted between the electrophotographic photosensitive member 109 and a transfer device (transfer means) 114 facing the electrophotographic photosensitive member 109 (transfer process). In addition, fixing is performed by heat and / or pressure of the fixing device 118 (fixing step). On the other hand, the residual toner on the surface of the electrophotographic photosensitive member 109 after the transfer is removed by a cleaning device (cleaning means) 116 provided with a cleaning blade 119 (cleaning step). Then, before proceeding to the next image forming cycle, the residual potential on the surface of the electrophotographic photosensitive member 109 is removed by the static eliminator 117.

  In the image forming apparatus as described above, since the magnetic toner of the present invention is used as the toner and the developing apparatus of the present invention is used as the developing means, the stress on the carrier is reduced and the life of the developer is extended. Therefore, a stable image can be formed and high reliability can be realized while being small and low cost.

(Toner recycling mechanism)
The present invention cleans the surface of the latent electrostatic image bearing member after transfer to collect the toner remaining on the surface of the latent electrostatic image bearing member, and supplies the collected toner to a developing device for use in the developing process. The present invention can also be suitably applied to an image forming apparatus including a configuration. By providing such a toner recycling mechanism (toner returning means), it is possible to reduce the environmental load due to toner disposal and to eliminate the need for a waste toner box, which is advantageous for making the machine compact.

Conventionally, toner is embedded or detached due to stress caused by agitation with the carrier, or its shape is likely to change. Even if the residual toner on the surface of the latent image carrier is reused, the state of the external additive and the shape of the toner are greatly different between the unused toner and the cleaning / collecting toner. Therefore, the toner replenishment property, charging property, etc. are greatly different between the two, which causes image quality problems such as a decrease in density and a deterioration in fine line reproducibility, and it is difficult to reuse the cleaning recovered toner. It was.
However, since the magnetic toner of the present invention has reduced stress due to stirring with the carrier, there is almost no change in characteristics between the unused toner and the cleaning / collecting toner, and the occurrence of image quality problems can be greatly suppressed. it can.

  FIG. 3 shows a schematic diagram of a main part of an example of an image forming apparatus having such a configuration. FIG. 3 is drawn with only the electrostatic latent image carrier, the developing device, and the cleaning means extracted from the image forming apparatus. Of course, this example also includes all the components shown in FIG. 2 as an image forming apparatus, and the members omitted in FIG. 3 have basically the same functions and functions as those shown in FIG. It has an action.

  That is, the image forming apparatus shown in FIG. 3 uses a developing device main body 15 ′ obtained by improving the developing device main body 15 with respect to the image forming apparatus shown in FIG. And a toner recycling mechanism (toner returning means). In FIG. 3, each member in the developing device main body 15 ′ is not given a reference numeral, but all the same members as those in the developing device main body 15 in FIG. 1 are provided, and their functions and operations are also the same. Therefore, the description thereof will be omitted together with the reference numerals.

  The toner remaining on the surface of the electrophotographic photosensitive member (electrostatic latent image carrier) 9 after the transfer of the toner image is scraped off by the cleaning blade 19 in the cleaning device (cleaning means) 16 and has no toner recycling mechanism. Is accommodated in the container 21.

  The toner recycling mechanism includes a recovery screw 22 that recovers the cleaning recovery toner and a transport screw 23 that transports the cleaning toner to the developing device main body 15 ′. That is, the cleaning recovery toner scraped off by the cleaning blade 19 is recovered by the recovery screw 22 and sent to the transport screw 23, and the toner storage section (reference numeral 5 in FIG. 1) in the developing device main body 15 ′ is sequentially transported by the transport screw 23. Are transported and supplied. In the toner storage unit, the cleaning-recovered toner and new toner are mixed and recycled (the toner returning step).

  In addition to the above example, the surface of the latent electrostatic image bearing member after the transfer is cleaned to collect the toner remaining on the surface of the latent electrostatic image bearing member, and the collected toner is conveyed to a developing device for the developing process. As the mechanism (toner returning means) to be used, other known methods can be adopted. Known methods include, for example, methods disclosed in JP-A-63-163883, JP-A-3-089289, and the like.

[Image forming method]
The image forming method of the present invention includes a developer carrying member having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier, and development for supplying the developer to the developer carrying member. A developer container, and a toner container that communicates with the developer container and accommodates toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, An image forming method using a developing device having a mechanism for autonomously controlling the toner intake of a two-component developer by changing the toner density of the two-component developer on the surface of the developer carrying member, wherein the toner is The magnetic toner of the present invention as described above.
Details of the configuration are as described in detail in the sections [Developing apparatus] and [Toner].

As an image forming method of the present invention,
(1) a latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
(2) The latent image formed is visualized by a two-component developer containing toner and magnetic carrier contained in the developing device, and a toner image is formed on the surface of the electrostatic latent image carrier. A development process to
(3) a transfer step of transferring the formed toner image to the surface of the transfer target;
(4) a cleaning step of cleaning the surface of the latent electrostatic image bearing member after transfer to recover toner remaining on the surface of the latent electrostatic image bearing member;
(5) a toner returning step of conveying the collected toner to the developing device;
It is also preferable to have a so-called toner recycling mechanism including
Details of the configuration are as described in detail in the section [Image forming apparatus].

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited only to these Examples.
In addition, the average particle diameter (center particle diameter) of the resin particles, the colorant particles, and the release agent particles was measured using a laser diffraction particle size distribution measuring device (manufactured by Horiba, Ltd .: LA-700). The molecular weight of the resin in the resin particles and toner particles was measured using gel permeation chromatography (manufactured by Tosoh Corporation: HLC-8120GPC).

(Preparation of resin fine particle dispersion (1))
・ Styrene (manufactured by Wako Pure Chemical Industries, Ltd.): 330 parts by mass. Nbutyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.): 70 parts by mass. Β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.): 9 parts by mass. Decanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.): 1.5 parts by mass / dodecanethiol (manufactured by Wako Pure Chemical Industries, Ltd.): 2.7 parts by mass

The above components were mixed and dissolved to prepare 413.2 parts by mass of a raw material solution. Separately, 4 parts by weight of an anionic surfactant (Dowfax, Rhodia) dissolved in 550 parts by weight of ion-exchanged water is added to the raw material solution, dispersed and emulsified in a flask, and stirred slowly for 10 minutes. -While mixing, 50 parts by mass of ion-exchanged water in which 6 parts by mass of ammonium persulfate was dissolved was added. Next, after sufficiently replacing the inside with nitrogen, the flask was heated with an oil bath while stirring until the inside of the system reached 70 ° C., and emulsion polymerization was continued for 5 hours to obtain an anionic resin fine particle dispersion ( 1) was obtained.
The obtained resin fine particles had a center particle size of 210 nm, a solid content of 40% by mass, a glass transition point of 52.0 ° C., and a mass average molecular weight Mw = 32000.

(Preparation of resin fine particle dispersion (2))
・ Styrene (manufactured by Wako Pure Chemical Industries, Ltd.): 330 parts by mass. Nbutyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.): 70 parts by mass. Β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.): 9 parts by mass. Decanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.): 1.2 parts by mass

The above components were mixed and dissolved to prepare 410.2 parts by mass of a raw material solution. Separately, 8 parts by weight of an anionic surfactant (Dowfax, Rhodia Co., Ltd.) dissolved in 550 parts by weight of ion-exchanged water was added to the raw material solution, dispersed and emulsified in a flask, and stirred slowly for 10 minutes. -While mixing, 50 parts by mass of ion-exchanged water in which 3 parts by mass of ammonium persulfate was dissolved was added. Next, after sufficiently replacing the inside with nitrogen, the flask was heated with an oil bath while stirring until the inside of the system reached 65 ° C., and emulsion polymerization was continued as it was for 5 hours to obtain an anionic resin fine particle dispersion ( 2) was obtained.
The obtained resin fine particles had a center particle size of 200 nm, a solid content of 40% by mass, a glass transition point of 54.0 ° C., and a mass average molecular weight Mw = 810000.

(Preparation of magnetic dispersion)
Magnetite (manufactured by Toda Kogyo Co., Ltd., saturation magnetization 84 Am ² / g at a particle size of 160 nm, 398 kA / m): 25 parts by mass Ionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku): 5 parts by mass : 70 parts by mass

After mixing the above components and pre-dispersing for 10 minutes with a homogenizer (Ultra Turrax, manufactured by IKA), dispersion treatment was performed at a pressure of 245 MPa for 15 minutes using a counter impact type wet pulverizer (Ultimizer, manufactured by Sugino Machine). To obtain a magnetic dispersion.
The central particle size of the magnetic substance in the obtained magnetic substance dispersion was 270 nm.

(Preparation of colorant dispersion)
・ Carbon black (R330, manufactured by Cabot): 25 parts by mass ・ Ionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku): 5 parts by mass ・ Ion-exchange water: 70 parts by mass

After mixing the above components and pre-dispersing for 10 minutes with a homogenizer (Ultra Turrax, manufactured by IKA), dispersion treatment was performed at a pressure of 245 MPa for 15 minutes using a counter impact type wet pulverizer (Ultimizer, manufactured by Sugino Machine). To obtain a colorant dispersion.
The center particle diameter of the colorant in the obtained colorant dispersion was 150 nm.

(Preparation of release agent dispersion)
-Polyethylene wax (PW850, manufactured by Toyo Petrolite Co., Ltd.): 200 parts by mass-Ionic surfactant (Neogen RK, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 10 parts by mass-Ion-exchanged water: 630 parts by mass

After the above components were heated to 130 ° C., a dispersion treatment was performed for 30 minutes under a pressure of 560 kg / cm ² using a Gorin homogenizer (manufactured by Gorin). Then, it cooled to 50 degreeC and the mold release agent dispersion liquid was obtained.
The center particle diameter of the release agent in the obtained release agent dispersion was 200 nm, and the solid content concentration was 25% by mass.

[Preparation of Magnetic Toner (1)]
-Resin fine particle dispersion (1): 80 parts by mass-Resin fine particle dispersion (2): 20 parts by mass-Magnetic substance dispersion: 48 parts by mass-Colorant dispersion: 20 parts by mass-Release agent dispersion: 36 Parts by mass

The above components were sufficiently mixed and dispersed in a round stainless steel flask using Ultra Turrax (T50, manufactured by IKA). Next, 0.36 parts by mass of polyaluminum chloride was added to the obtained dispersion, and the dispersion operation was continued with an ultra turrax.
Thereafter, the flask was heated to 51 ° C. with stirring in an oil bath for heating. After maintaining at 51 ° C. for 60 minutes, 35 parts by mass of resin fine particle dispersion (1) was gradually added. Thereafter, the pH of the system was adjusted to 5.4 with a 0.5 N aqueous sodium hydroxide solution, and then the stainless steel flask was sealed and heated to 95 ° C. while continuing to stir using a magnetic seal for 5 hours. Retained.

After completion of the reaction, the mixture was cooled, filtered, thoroughly washed with ion exchange water, and then subjected to solid-liquid separation by Nutsche suction filtration.
The separated solid was further redispersed in 3 liters of ion-exchanged water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This was repeated 5 times, and No. 1 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain magnetic black particles.

To 100 parts by mass of the magnetic black particles, 1.5 parts by mass of dimethyl silicone oil-treated silica (RY200: manufactured by Nippon Aerosil Co., Ltd., primary particle diameter: 12 nm) is added, mixed and externally added using a Henschel mill. A magnetic toner (1) used in Example 1 was obtained.
The obtained magnetic toner (1) has a volume average particle diameter D _50v of 7.0 μm, a shape factor SF-1 of 131, and a distance from the toner surface to the nearest magnetic surface (distance D _min ) of 0.1 μm or less. The number of toner particles is 7% by number, the saturation magnetization σs at 398 kA / m is 13 Am ² / kg, and the amount of surface wax by XPS is 24%. (The same applies to other toners.)

Here, a specific method for measuring the volume average particle diameter D _50v and the shape factor SF-1 of the toner will be described. The same applies to other toners.
The volume average particle diameter D _50v of the toner was measured using a Coulter Counter TA-II. In the measurement, ISOTON-II (manufactured by Beckman Coulter, Inc.) was used as the electrolyte. The number of particles measured is 50000 per sample.
The toner shape factor SF-1 was determined by the above-described method using a Luzex image analyzer (manufactured by Nireco Corporation, LUZEX III).

[Preparation of Magnetic Toner (2)]
In [Preparation of magnetic toner (1)], the amount of the resin fine particle dispersion (1) added was changed from 35 parts by mass to 40 parts by mass after being held at 51 ° C. for 60 minutes by a heating oil bath. The magnetic toner (2) used in Example 2 was obtained in the same manner as the magnetic toner (1).
The obtained magnetic toner (2) has a volume average particle diameter D _50v of 7.1 μm, a shape factor SF-1 of 128, and 5% by number of toner particles having a distance D _min of 0.1 μm or less at 398 kA / m. The saturation magnetization σs was 13 Am ² / kg, and the surface wax amount by XPS was 17%.

[Preparation of magnetic toner (3)]
-Resin fine particle dispersion (1): 80 parts by mass-Resin fine particle dispersion (2): 20 parts by mass-Magnetic substance dispersion: 90 parts by mass-Colorant dispersion: 6 parts by mass-Release agent dispersion: 40 Parts by mass

The above components were sufficiently mixed and dispersed in a round stainless steel flask using Ultra Turrax (T50, manufactured by IKA). Next, 0.4 parts by mass of polyaluminum chloride was added to the obtained dispersion, and the dispersion operation was continued with an ultra turrax.
Thereafter, the flask was heated to 50 ° C. with stirring in an oil bath for heating. After maintaining at 50 ° C. for 80 minutes, 40 parts by mass of the resin fine particle dispersion (1) was gradually added. Thereafter, the pH of the system was adjusted to 5.2 with a 0.5 N aqueous sodium hydroxide solution, and then the stainless steel flask was sealed and heated to 95 ° C. while continuing to stir using a magnetic seal for 6 hours. Retained.

Thereafter, washing, drying and external addition were performed in the same manner as the magnetic toner (1) to obtain the magnetic toner (3) used in Example 3.
The obtained magnetic toner (3) has a volume average particle diameter _D50v of 6.6 μm, a shape factor SF-1 of 125, and 13% by number of toner particles having a distance _Dmin of 0.1 μm or less at 398 kA / m. The saturation magnetization σs was 21 Am ² / kg, and the surface wax amount by XPS was 21%.

[Preparation of Magnetic Toner (4)]
-Resin fine particle dispersion (1): 80 parts by mass-Resin fine particle dispersion (2): 20 parts by mass-Magnetic substance dispersion: 104 parts by mass-Release agent dispersion: 40 parts by mass

The above components were sufficiently mixed and dispersed in a round stainless steel flask using Ultra Turrax (T50, manufactured by IKA). Next, 0.48 parts by mass of polyaluminum chloride was added to the obtained dispersion, and the dispersion operation was continued with an ultra turrax.
Thereafter, the flask was heated to 51 ° C. with stirring in an oil bath for heating. After maintaining at 51 ° C. for 60 minutes, 60 parts by mass of resin fine particle dispersion (1) was gradually added. Thereafter, the pH of the system was adjusted to 5.3 with a 0.5 N aqueous sodium hydroxide solution, and then the stainless steel flask was sealed, and heated to 95 ° C. while continuing to stir using a magnetic seal for 5 hours. Retained.

Thereafter, washing, drying and external addition were carried out in the same manner as the magnetic toner (1) to obtain the magnetic toner (4) used in Example 4.
The obtained magnetic toner (4) has a volume average particle diameter D _50v of 7.0 μm, a shape factor SF-1 of 135, and toner particles having a distance D _min of 0.1 μm or less at 22% by number and 398 kA / m. The saturation magnetization σs was 22 Am ² / kg, and the surface wax amount by XPS was 25%.

[Preparation of Magnetic Toner (5)]
In [Preparation of magnetic toner (1)], the amount of the resin fine particle dispersion (1) added was changed from 35 parts by mass to 30 parts by mass after being held at 51 ° C. for 60 minutes by a heating oil bath. The magnetic toner (5) used in Example 5 was obtained in the same manner as the magnetic toner (1).
The obtained magnetic toner (5) has a volume average particle diameter D _50v of 6.8 μm, a shape factor SF-1 of 135, and toner particles having a distance D _min of 0.1 μm or less at 34% by number and 398 kA / m. The saturation magnetization σs was 13 Am ² / kg, and the surface wax amount by XPS was 42%.

[Preparation of Magnetic Toner (6)]
The resin fine particle dispersion (1) and the resin fine particle dispersion (2) were respectively washed to remove the surfactant and then dried to obtain a dried resin fine particle (1) and a dried resin fine particle (2). Using the obtained dried resin fine particles, a magnetic toner (6) was produced as follows.
-Dry resin fine particles (1): 57.5 parts by mass-Dry resin fine particles (2): 10.0 parts by mass-Magnetite (manufactured by Toda Kogyo Co., Ltd., saturation magnetization 84 Am ² / g at a particle size of 160 nm, 398 kA / m ): 15.0 parts by mass, carbon black (R330, manufactured by Cabot Corporation): 6.3 parts by mass, polyethylene wax (PW850, manufactured by Toyo Petrolite): 11.3 parts by mass

The above ingredients were mixed with powder using a Henschel mixer, and this was heat-kneaded using an extruder with a set temperature of 160 ° C. After cooling, coarsely and finely pulverized, and the pulverized product was classified to obtain magnetic black particles.
To 100 parts by mass of the obtained black particles, 1.5 parts by mass of dimethyl silicone oil-treated silica (RY200: manufactured by Nippon Aerosil Co., Ltd., primary particle size: the same as above) is added, mixed using a Henschel mill, and externally added. A magnetic toner (6) used in Comparative Example 1 was obtained.
The obtained magnetic toner (6) has a volume average particle diameter D _50v of 7.0 μm, a shape factor SF-1 of 147, and toner particles having a distance D _min of 0.1 μm or less at 75% by number and 398 kA / m. The saturation magnetization σs was 13 Am ² / kg, and the surface wax amount by XPS was 55%.

[Preparation of magnetic toner (7)]
In [Preparation of Magnetic Toner (1)], the pH value in the system adjusted after adding the resin fine particle dispersion (1) is adjusted from 5.4 to 5.1, the stainless steel flask is sealed, and the magnetic force is The magnetic toner (7) used in Comparative Example 2 is the same as the magnetic toner (1) except that the holding time at 95 ° C., which is performed while continuing the stirring using the seal, is changed from 5 hours to 2.5 hours. Got.
The obtained magnetic toner (7) has a volume average particle diameter D _50v of 6.8 μm, a shape factor SF-1 of 135, and toner particles having a distance D _min of 0.01 μm or less at 54% by number and 398 kA / m. The saturation magnetization σs was 13 Am ² / kg, and the amount of surface wax by XPS was 45%.

[Preparation of Magnetic Toner (8)]
In [Preparation of magnetic toner (1)], the amount of the resin fine particle dispersion (1) added was changed from 35 parts by mass to 55 parts by mass after being held at 51 ° C. for 60 minutes by a heating oil bath. The magnetic toner (8) used in Comparative Example 3 was obtained in the same manner as the magnetic toner (1). The obtained magnetic toner (8) had a volume average particle diameter D _50v of 7.2 μm and a shape factor SF-1 of The number of toner particles with 127 and distance D _min of 0.1 μm or less was 0%, the saturation magnetization σs at 398 kA / m was 11 Am ² / kg, and the surface wax amount by XPS was 12%.

[Preparation of Magnetic Toner (9)]
In [Preparation of Magnetic Toner (1)], the pH value in the system to be adjusted after adding the resin fine particle dispersion (1) is adjusted from 5.4 to 4.9, the stainless steel flask is sealed, and the magnetic force is The magnetic toner (9) used in Example 6 is obtained in the same manner as the magnetic toner (1) except that the holding time at 95 ° C., which is performed while continuing the stirring using the seal, is changed from 5 hours to 10 hours. It was.
The obtained magnetic toner (9) has a volume average particle diameter D _50v of 7.0 μm, a shape factor SF-1 of 109, and 15% toner particles having a distance D _min of 0.1 μm or less at 398 kA / m. The saturation magnetization σs was 13 Am ² / kg, and the surface wax amount by XPS was 12%.

[Preparation of Magnetic Toner (10)]
-Resin fine particle dispersion (1): 80 parts by mass-Resin fine particle dispersion (2): 20 parts by mass-Magnetic substance dispersion: 14 parts by mass-Colorant dispersion: 16 parts by mass-Release agent dispersion: 30 Parts by mass

The above components were sufficiently mixed and dispersed in a round stainless steel flask using Ultra Turrax (T50, manufactured by IKA). Next, 0.4 parts by mass of polyaluminum chloride was added to the obtained dispersion, and the dispersion operation was continued with an ultra turrax.
Thereafter, the flask was heated to 50 ° C. with stirring in an oil bath for heating. After maintaining at 50 ° C. for 80 minutes, 25 parts by mass of the resin fine particle dispersion (1) was gradually added. Thereafter, the pH of the system was adjusted to 5.2 with a 0.5 N aqueous sodium hydroxide solution, and then the stainless steel flask was sealed, and heated to 95 ° C. while continuing to stir using a magnetic seal for 4 hours. Retained.

Thereafter, washing, drying, and external addition were performed in the same manner as the magnetic toner (1) to obtain the magnetic toner (10) used in Comparative Example 4.
The obtained magnetic toner (10) has a volume average particle diameter D _50v of 6.7 μm, a shape factor SF-1 of 130, and 4% by number of particles having a distance D _min of 0.1 μm or less, a saturation magnetization at 398 kA / m. σs was 4.5 Am ² / kg, and the surface wax amount by XPS was 22%.

[Preparation of Magnetic Toner (11)]
-Resin fine particle dispersion (1): 80 parts by mass-Resin fine particle dispersion (2): 20 parts by mass-Magnetic substance dispersion: 280 parts by mass-Release agent dispersion: 60 parts by mass

The above components were sufficiently mixed and dispersed in a round stainless steel flask using Ultra Turrax (T50, manufactured by IKA). Next, 0.4 parts by mass of polyaluminum chloride was added to the obtained dispersion, and the dispersion operation was continued with an ultra turrax.
Thereafter, the flask was heated to 51 ° C. with stirring in an oil bath for heating. After maintaining at 51 ° C. for 100 minutes, 45 parts by mass of resin fine particle dispersion (1) was gradually added. Thereafter, the pH of the system was adjusted to 5.0 with a 0.5 N aqueous sodium hydroxide solution, and then the stainless steel flask was sealed and heated to 95 ° C. while continuing to stir using a magnetic seal for 7 hours. Retained.

Thereafter, washing, drying and external addition were performed in the same manner as the magnetic toner (1) to obtain the magnetic toner (11) used in Comparative Example 5.
The magnetic toner (11) thus _obtained has a volume average particle diameter D _50v of 6.8 μm, a shape factor SF-1 of 128, and particles having a distance D _min of 0.1 μm or less, 34% by number, and saturation magnetization at 398 kA / m. σs was 41 Am ² / kg, and the surface wax amount by XPS was 18%.

[Production of carrier]
Mn-Mg ferrite particles (average particle size 35 μm): 100 parts by mass Toluene: 11 parts by mass Diethylaminoethyl methacrylate-styrene-methyl methacrylate copolymer (copolymerization ratio 2:20:78, mass average molecular weight 50, 000): 2 parts by mass / carbon black (manufactured by Cabot, R330R): 0.2 parts by mass

The above components excluding Mn-Mg based ferrite particles and glass beads (particle size: 1 mm, equivalent to toluene) were put into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred for 30 minutes at a rotational speed of 1200 rpm to obtain a coating resin layer forming solution. Was prepared.
Next, the coating resin layer forming solution and the Mn-Mg ferrite particles are placed in a vacuum degassing kneader, stirred for 10 minutes while maintaining a temperature of 60 ° C., and then the toluene is distilled off under reduced pressure. A coating resin layer was formed to obtain a carrier.

[Preparation of Developers (1) to (11)]
20 parts by mass of magnetic toners (1) to (11) are added to 100 parts by mass of the carrier and stirred and mixed in a ball mill for 5 minutes to obtain developers (1) to (11) as magnetic two-component developers. Obtained.

[Example 1]
<Evaluation 1>
As the developing device (Evaluation 1) used in this example, the developing device shown in FIG. 1 was used. Detailed specifications are as follows.
Fixed magnet 1: A four-pole magnetic pole is provided, and the two-component developer 2 is magnetically attached to the outer periphery of the developer carrier 3.
A φ16 mm metal sleeve having a 10-point average roughness Rz = 7 μm was used on the surface of the developer carrier 3 and the peripheral speed was set to 140 mm / s.
-Damping part 8: Set so that the gap with the surface of the developer carrier 3 was 400 μm.
Electrophotographic photoreceptor (electrostatic latent image carrier) 9: An organic photoreceptor having a diameter of 30 mm was used.
Developer developing member 10: A cylindrical magnetic body having a diameter of 70 mm was used, and the peripheral speed was set to 60 mm / s.
Toner stirring member 11: A PET film was used, and the peripheral speed was set to 20 mm / s.
Partition part 12: Set so that the gap with the surface of the developer carrier 3 was 3 mm.

In the developing device, the developer (1) is accommodated in the developer accommodating portions 4a and 4b, and the magnetic toner (1) is accommodated in the toner accommodating portion 5.
Further, the laser printer DocuPrint 255 manufactured by Fuji Xerox Co., Ltd. was modified so that it could be equipped with the above developing device, and this was deployed to produce the image forming apparatus (1) used in <Evaluation 1>.

(Evaluation test)
The image forming apparatus (1) was subjected to the following evaluation test. Evaluation was carried out in an environment of high temperature and high humidity (28 ° C., 90% RH). The results are summarized in Table 1 below.

1) Evaluation of maintainability of image density Initially, after printing 50000 sheets in A4 size on a chart with 5% image density, print a 100% black solid image in A4 size, and measure density with reflection densitometer X-Rite404 went. A difference ΔSAD in image density was obtained for the initial printing and after printing 50000 sheets and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: ΔSAD: less than 0.10 (a level that is completely satisfactory)
○: ΔSAD: 0.10 or more and less than 0.15 (practical problem level)
Δ: ΔSAD: 0.15 or more and less than 0.20 (partially problematic level)
×: ΔSAD: 0.20 or more (a level that causes a big problem)

2) Evaluation of image quality Initially and after printing 50000 sheets in A4 size on a chart with an image density of 5%, defects on the image of the fixed image were visually confirmed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
○: Level at which no defect occurs on the image.
(Triangle | delta): Although the defect | deletion has generate | occur | produced slightly on the image, it is a level which is satisfactory practically.
X: Defects are observed on the image, and this is a practically problematic level.

3) Evaluation of background stains The background stains of the blank paper after 1000 white paper images were output in A4 size were visually confirmed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
◯: Compared with the white paper before printing, it is a level at which scumming cannot be detected visually.
(Triangle | delta): Although it can detect slightly visually compared with the white paper before printing, it is a level which is satisfactory practically.
X: Compared with the white paper before printing, the occurrence of background stains can be clearly detected with the naked eye, and this is a practically problematic level.

<Evaluation 2>
The image forming apparatus (1) used in <Evaluation 1> is further modified to provide the image forming apparatus (2) used in <Evaluation 2> as the image forming apparatus shown in FIG. . Detailed specifications relating to the toner recycling mechanism are as follows.

The cleaning blade 19 is made of urethane rubber and is pressed against the electrophotographic photosensitive member (electrostatic latent image carrier) 9. The residual toner remaining on the surface of the electrophotographic photosensitive member 9 is cleaned and stored in the storage container 21. It is configured as follows. The toner in the container 21 is returned again to the developing device 15 ′ through the recovery screw 22 and the conveying screw 23.
Each of the recovery screw 22 and the conveying screw 23 is a spiral screw in which a single metal thin plate is wound around a metal round bar having a diameter of 5 mm, and is fixed at a pitch of 10 mm and an outer diameter of 12 mm, and rotates 10 times per minute. Adjusted as follows.

With respect to the image forming apparatus (2), first, a chart having an image density of 5% was printed on 5000 sheets in A4 size, and the cleaning recovered toner was returned to the developing device 15 ′ to be reused.
Subsequently, the same evaluation as 1) to 3) of <Evaluation 1> was performed. The results are summarized in Table 1 below.

[Examples 2-6, Comparative Examples 1-5]
In Example 1, the developer used is changed from the developer (1) to the developers (2) to (11), and the toner used is changed from the magnetic toner (1) so as to have the combinations shown in Table 1 below. Except for changing to the magnetic toners (2) to (11), the developing devices of the respective examples and comparative examples were produced in the same manner as in Example 1, and the image forming devices (1) and (2) were produced. Each was evaluated. The results are summarized in Table 1 below.

[Consideration of results]
As shown in Table 1 above, in Examples 1 to 5, in the developing device that autonomously controls the toner density, the magnetic toner or developer of the present invention is used, so that there is no decrease in image density, A high quality image with excellent uniformity can be obtained. Further, even when the toner collected for cleaning was reused, no problem with image density or image quality occurred.

In Example 5, since the toner surface wax amount exceeded 40%, the toner concentration maintenance level was slightly inferior but acceptable.
In Example 6, slight image defects due to poor cleaning were slightly observed, but there was no problem with image density, and the overall level was satisfactory.

On the other hand, in Comparative Example 1, the toner shape factor SF-1 and the ratio of the toner having a distance (D _min ) of 0.1 μm or less are out of the preferred range, so the image density maintainability is greatly inferior. As a result. Further, regarding the image quality, the reproducibility of fine lines was poor due to the scattering of toner, and characters were lost during transfer, resulting in poor image quality. Furthermore, in <Evaluation 2>, the reuse of the cleaning collected toner caused an even worse image quality defect, and scumming appeared to be caused by the unstable charging property of the cleaning collected toner.

In Comparative Examples 2 and 3, since the ratio of the toner shape factor SF-1 and the distance (D _min ) is 0.1 μm or less is out of the scope of the present invention, there is a problem in image density maintenance and image quality. Further deterioration was observed when the toner collected for cleaning was reused.

In Comparative Example 4, since the saturation magnetization σs at 398 kA / m was low, the occurrence of background staining was observed.
In Comparative Example 5, since the saturation magnetization σs at 398 kA / m was too large, the stress on the carrier was large, and the density after 50000 sheets was lowered in the evaluation of image density maintenance.

1 is a schematic cross-sectional view illustrating an outline of a developing device which is an example of the present invention. 1 is a schematic cross-sectional view illustrating an outline of an image forming apparatus which is an example of the present invention. FIG. 6 is a schematic cross-sectional view illustrating an outline of an image forming apparatus including an autonomous toner density control mechanism that is another example of the present invention.

Explanation of symbols

  1: fixed magnet, 2: two-component developer, 3: developer carrier, 4a: first developer container, 4b: second developer container, 5: toner container, 6: developer supply port, 7: Developer retracting section, 8: Damping section, 9, 109: Electrophotographic photosensitive member (electrostatic latent image carrier), 10: Developer stirring member, 11: Toner stirring member, 12: Partition section, 15: Development Device main body, 15 ': Developing device, 19, 119: Cleaning blade, 21: Container, 22: Collection screw, 23: Conveying screw, 111: Charger, 113: Image input device (latent image forming means), 114: Transfer device (transfer device) 116: Cleaning device (cleaning device) 117: Static eliminator 118: Fixing device 120: Transfer object T: Toner

Claims (9)

A developer carrying body having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier; a developer containing portion for supplying the developer to the developer carrying body; and the developer A toner containing portion that communicates with the containing portion and contains the toner, and the amount of the two-component developer carried on the developer carrying member is regulated by a regulating member, and two on the surface of the developer carrying member. Toner used in a developing device having a mechanism for autonomously controlling toner intake of a two-component developer according to a change in toner concentration of the component developer,
A magnetic toner containing at least a binder resin, a magnetic material, and a release agent;
Its shape factor SF-1 is 140 or less,
The toner having a distance (D _min ) from the toner surface to the nearest magnetic material surface of 0.1 μm or less is 1% by weight or more and less than 50% by weight in all toners,
The saturation magnetization σs at 398 kA / m is 5 to 40 Am ² / kg,
A magnetic toner characterized by being. 2. The magnetic toner according to claim 1, wherein a surface wax amount by XPS is 5 to 40%. 3. The magnetic toner according to claim 1, wherein the magnetic toner is manufactured by a wet manufacturing method. A developer carrying member having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier; a developer containing portion for supplying the developer to the developer carrying member; and the developer A toner containing portion that communicates with the containing portion and contains the toner, and the amount of the two-component developer carried on the developer carrying member is regulated by a regulating member, and two on the surface of the developer carrying member. A two-component developer used in a developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner concentration of the component developer,
A two-component developer, wherein the toner contained is the magnetic toner according to claim 1. A developer carrying body having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier; a developer containing portion for supplying the developer to the developer carrying body; and the developer A toner containing portion that communicates with the containing portion and contains the toner, and the amount of the two-component developer carried on the developer carrying member is regulated by a regulating member, and two on the surface of the developer carrying member. A developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner density of the component developer;
The developing device according to claim 1, wherein the toner stored in the toner storage unit is the magnetic toner according to claim 1. The latent image formed by at least a latent image forming means for forming an electrostatic latent image on the surface of the electrostatic latent image carrier and a two-component developer containing toner and a magnetic carrier housed in the developing device. Image forming apparatus comprising: a developing unit that visualizes a toner image to form a toner image on the surface of the electrostatic latent image carrier; and a transfer unit that transfers the formed toner image to the surface of the transfer target Because
The developing device in the developing means includes a developer carrying body having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier, and development for supplying the developer to the developer carrying body A developer container, and a toner container that communicates with the developer container and accommodates toner, and the amount of the two-component developer carried on the developer carrier is regulated by a regulating member, A developing device having a mechanism for autonomously controlling the toner intake of the two-component developer by changing the toner density of the two-component developer on the surface of the developer carrying member, and is accommodated in the toner accommodating portion. An image forming apparatus, wherein the toner is the magnetic toner according to claim 1. And cleaning means for cleaning the surface of the electrostatic latent image carrier after transfer by the transfer means, and collecting toner remaining on the surface of the electrostatic latent image carrier;
The image forming apparatus according to claim 6, further comprising a toner returning unit that conveys the collected toner to the developing device. A developer carrying body having a magnetic field generating means therein and carrying and carrying a two-component developer containing toner and a magnetic carrier; a developer containing portion for supplying the developer to the developer carrying body; and the developer A toner containing portion that communicates with the containing portion and contains the toner, and the amount of the two-component developer carried on the developer carrying member is regulated by a regulating member, and two on the surface of the developer carrying member. An image forming method using a developing device having a mechanism for autonomously controlling the toner intake of a two-component developer by changing the toner density of the component developer,
An image forming method, wherein the toner is the magnetic toner according to claim 1. A latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
A developing step of forming the toner image on the surface of the electrostatic latent image carrier by visualizing the formed latent image with a two-component developer containing toner and magnetic carrier contained in the developing device. When,
A transfer step of transferring the formed toner image onto the surface of the transfer target;
A cleaning step of cleaning the surface of the latent electrostatic image bearing member after transfer to recover toner remaining on the surface of the latent electrostatic image bearing member;
A toner returning step of conveying the collected toner to the developing device;
The image forming method according to claim 8, further comprising:

Images